The invention relates generally to drive assemblies for superchargers and more specifically to a continuously variable drive assembly for optimizing the speed of a supercharger driven by an internal combustion engine.
Increasing the volume of air provided to the cylinders of an internal combustion engine during its intake cycle and thereby increasing the density of the air during the compression and ignition strokes has long been recognized as a means of increasing the horsepower output of an internal combustion engine. Two classes of equipment have been relied upon to achieve this goal: turbochargers and superchargers. Turbochargers are defined as devices of the class which are driven by a turbine exposed to the exhaust gasses of the engine to which the turbocharger is providing increased air pressure. Likely the most common and widely recognized issue with a turbocharger is what is referred to as turbo lag. Since the turbocharger depends upon an engine's exhaust gasses to drive it and increase its speed, when increased power output of the engine is desired, the turbocharger cannot increase its speed to increase engine performance until the flow of exhaust gasses increases to increase its rotational speed. Thus, inherent in the design is a delay from the feedback nature of the device. While there are design approaches which reduce turbo lag such as minimizing the rotating mass of the turbocharger, turbo lag remains a concomitant to turbocharger designs.
Superchargers, on the other hand, achieve a similar goal, but rather than being driven by engine exhaust gasses, they are driven directly by a fan belt or belt which is driven by the crankshaft pulley. In this configuration, as the speed of the engine increases, the speed of the supercharger immediately and proportionally increases. Hence, the problem of turbo lag is essentially eliminated. However, due to the wide variation in engine speed, typically from 700–800 R.P.M. at idle to 6,000–8,000 R.P.M. or higher at red line, a supercharger is subjected to a wide variation in drive speeds. This wide variation interferes with optimum operation as many supercharger designs provide their best performance enhancing capabilities when driven at a constant or substantially constant speed.
Attempts have been made to achieve this goal. For example, U.S. Pat. No. 5,462,035 teaches a supercharger which is driven through a continuously variable transmission (CVT) comprising a pair of variable diameter pulleys interconnected by a belt. The present invention is directed to a drive assembly for a supercharger which maintains a substantially constant supercharger drive speed notwithstanding variations in the speed of the associated internal combustion engine.